1. Patients with a body mass index (BMI) of 40 kg/m2 or greater who had total knee replacement surgery improved quality-adjusted life expectancy at an acceptable cost.
2. Treatment was less cost-effective for older patients and those with prognostically important comorbidities such as diabetes and cardiovascular disease.
Evidence Rating Level: 2 (Good)
Study Rundown: Total knee replacement (TKR) is a highly utilized treatment option that has been shown to improve pain, function, and overall quality of life in patients with end-stage knee osteoarthritis. The American Association of Hip and Knee Surgeons suggests those with a BMI > 40kg/m2 may have complication profiles that outweigh the treatment benefits. However, other studies have shown that patient-reported outcomes are similar between this group and nonobese patients. This modeling study assessed the value of TKR in morbidly obese patients while accounting for increased rates of perioperative complications and mortality. The study determined younger patients who received TKR were projected to have a quality-adjusted life expectancy (QALE) that was nearly one year longer than those who did not receive TKR. The total difference in medical costs amounted to roughly $25,000. Older patients who received TKR had lower costs compared to the younger cohort but also saw a smaller increase in QALE. These findings were robust, with the costs of TKR remaining below the willingness-to-pay threshold of $55,000 for older and younger patients.
Relevant Reading: National obesity trends in total knee arthroplasty
In-Depth [prospective cohort]: The Osteoarthritis Policy (OAPol) Model was used to simulate the individual natural histories and treatments of one million persons. Demographic and clinical characteristics such as BMI, pain, and comorbidities were assigned based on user-defined distributions informed by published data. Projected quality-of-life was stratified by obesity, knee pain, age, number of comorbidities, and treatment-related complications. In the base-case analysis, patients aged 50 to 65 years with a BMI of 40 kg/m2 or greater had an increase in QALE from 9.3 years to 10.1 years after receiving TKR. The total costs increased by $25,200, corresponding to an incremental cost-effectiveness ratio (ICER) of $35,200 per quality-adjusted life year (QALY). Patients over the age of 65 years with a BMI of 40 kg/m2 or greater had an increase in QALE from 6.3 years to 6.7 years at a cost of $21,100, corresponding to an ICER of $54,100 per QALY. Patients with comorbidities had significantly higher costs compared to those who did not; for instance, the ICER for patients over the age of 65 who had both diabetes mellitus and cardiovascular disease was $71,100 as compared to an ICER of $46,900 for those who had neither. ICERs remained below $100,000 in all sensitivity analyses except when complication probabilities increased 7-fold in patients older than 65 years. Overall, patients with a BMI > 40kg/m2 and knee osteoarthritis improved QALE with an acceptable cost.
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